title: Digoxin net secretory transport in bronchial epithelial cell layers is not exclusively mediated by P-glycoprotein/MDR1.
abstract: The impact of P-glycoprotein (MDR1, ABCB1) on drug disposition in the lungs as well as its presence and activity in in vitro respiratory drug absorption models remain controversial to date. Hence, we characterised MDR1 expression and the bidirectional transport of the common MDR1 probe (3)H-digoxin in air-liquid interfaced (ALI) layers of normal human bronchial epithelial (NHBE) cells and of the Calu-3 bronchial epithelial cell line at different passage numbers. Madin-Darby Canine Kidney (MDCKII) cells transfected with the human MDR1 were used as positive controls. (3)H-digoxin efflux ratio (ER) was low and highly variable in NHBE layers. In contrast, ER=11.4 or 3.0 were measured in Calu-3 layers at a low or high passage number, respectively. These were, however, in contradiction with increased MDR1 protein levels observed upon passaging. Furthermore, ATP depletion and the two MDR1 inhibitory antibodies MRK16 and UIC2 had no or only a marginal impact on (3)H-digoxin net secretory transport in the cell line. Our data do not support an exclusive role of MDR1 in (3)H-digoxin apparent efflux in ALI Calu-3 layers and suggest the participation of an ATP-independent carrier. Identification of this transporter might provide a better understanding of drug distribution in the lungs.
authors.affiliation: Division of Drug Delivery and Tissue Engineering, School of Pharmacy, University of Nottingham, UK.
authors.forename: Victoria
authors.initials: V
authors.lastname: Hutter
authors.affiliation: Allergy Research Group, School of Molecular Medical Sciences, University of Nottingham, UK.
authors.forename: David Y S
authors.initials: DY
authors.lastname: Chau
authors.affiliation: AstraZeneca R&D, Mölndal, Sweden.
authors.forename: Constanze
authors.initials: C
authors.lastname: Hilgendorf
authors.affiliation: Immune Modulation Group, Division of Molecular and Cellular Science, School of Pharmacy, University of Nottingham, UK.
authors.forename: Alan
authors.initials: A
authors.lastname: Brown
authors.affiliation: AstraZeneca R&D Charnwood, Loughborough, UK.
authors.forename: Anne
authors.initials: A
authors.lastname: Cooper
authors.affiliation: AstraZeneca R&D Charnwood, Loughborough, UK.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Zann
authors.affiliation: Immune Modulation Group, Division of Molecular and Cellular Science, School of Pharmacy, University of Nottingham, UK.
authors.forename: David I
authors.initials: DI
authors.lastname: Pritchard
authors.affiliation: Division of Drug Delivery and Tissue Engineering, School of Pharmacy, University of Nottingham, UK. Electronic address: cynthia.bosquillon@nottingham.ac.uk.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Bosquillon
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D001980:Bronchi / Q000166:cytology / Q000378:metabolism*; D018929:Cell Culture Techniques; D004077:Digoxin / Q000378:metabolism / Q000493:pharmacokinetics*; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D061985:Madin Darby Canine Kidney Cells; D018613:Microscopy, Confocal; D010539:Permeability; D014162:Transfection
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004077:Digoxin
keywords: Bronchial epithelium; Calu-3; Drug transporters; In vitro models; In vitro/in vivo correlation; Pulmonary absorption